New York — About a year and half ago, New Jersey Gov. Chris Christie’s close-knit team had a carefully thought-out plan to prove his bipartisan mettle and show how a Republican could dominate a state of Democratic blue.

Governor Christie had one of the more talented young campaign managers, Bill Stepien, who helped orchestrate his landslide win in 2013 and was mapping a nationwide path toward the prize of 2016. And with a tell-it-as-it-is tough-guy Jersey panache, Christie was set to head the Republican Governors Association, crisscrossing the country and raising oodles of cash for fellow GOP heads of US states. With a pocketful of favors and political capital to spare, they hoped, he could prove he could carry the Republican torch with broad bipartisan appeal.

And then: “Time for some traffic problems in Fort Lee.” It was a text from Christie’s close deputy, Bridget Kelly, an aide at the governor’s side most of the time. “Got it,” replied David Wildstein, a director at the Port Authority of New York and New Jersey, which runs the George Washington Bridge.

On Friday, Mr. Wildstein, a former high school classmate of Christie, pleaded guilty to the first charges handed down in the scandal. For 16 months, Paul Fishman, the US attorney for New Jersey, has been probing the actions of the governor’s team and the motives behind the lane closures that caused traffic problems in Fort Lee, N.J. The closures are widely presumed to be a dirty trick against the Fort Lee mayor, a Democrat who refused to join the bipartisan Christie slate of endorsements.

Christie said he barely knew Wildstein, who was appointed to his post by the governor’s close ally at the Port Authority, Bill Baroni. The chairman of the bi-state commission at the time, David Samson, was one of the governor's closest advisers and a long-term mentor.

“I don’t think that has anything much to do with me,” Christie said during a press conference in New Brunswick, N.J., on Wednesday. “That matter will take its natural course and will be dictated by the folks who are investigating it, and I don’t have anything to do with that.”

But Wildstein’s attorney suggested last year that “evidence exists” that the governor was aware of the lane closures. On Friday, political observers are set to see if such evidence will be presented, with Mr. Fishman holding a news conference at 1 p.m.

Christie has steadfastly denied that he knew anything of the closures at the time. But his original close-knit team has been decimated. Mr. Stepien, who knew of the closures offhand, resigned when the scandal began. Ms. Kelly, fired. At the Port Authority, Wildstein, Mr. Baroni, and Mr. Samson each resigned in measures of disgrace.

And Christie’s once-wild popularity in the state, as well as among fans across the country, has waned. Even though he broke records raising cash for Republican governors, his presidential fundraising is presumed to be tepid, just like his nationwide standings in polls. The once-promising path to 2016 has hardly gone according to plan.

“If Mr. Wildstein has given that evidence to the prosecutors, I think it’s the end of Christie’s presidential aspirations, and it may be the end of him as governor,” Matthew Hale, professor of political science at Seton Hall University in South Orange, N.J., told Bloomberg Business. “I don’t think he can recover from that.”